Use-after-free from a comparator that answers inconsistently

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

`OrderedSkipList`, `SkipSet` and `SkipMap` can free a node that is still linked when a `Comparator` or `Ord` implementation gives different answers for the same pair of values during one mutating call. A later call reads the freed memory (CWE-416). A safe `impl Ord` with the default comparator is enough to reach it. The mutating traversals record a precursor at each level: the last node whose link points at a node comparing not-`Less` than the target. The splice code assumes every recorded precursor's link points at or past the final position. If a later comparison reports one of those nodes as `Less`, the walk steps past it and the assumption breaks. Removals such as `take_first`, `take` and `remove` then rewire the wrong link and free the target while its real predecessor still points at it. `insert` builds crossed links and wrong skip distances from the same precursors. A comparator that is a pure function of its two arguments cannot trigger this, even if it is not transitive. The…

Published by the source

24 Oct 2026, 12:00 UTC

Last modified by the source

26 Oct 2026, 14:00 UTC

Source last checked

27 Oct 2026, 06:25 UTC

1. Revision 1 · created · 27 Oct 2026

   Published from osv record RUSTSEC-2026-0409

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# Patch Next advisory brief: GHSA-cc53-p78w-23w9

Advisory: Use-after-free from a comparator that answers inconsistently
IDs: GHSA-cc53-p78w-23w9
Record: https://patchnext.com/advisories/rustsec-2026-0409 (revision 1, source checked 27 Oct 2026, 06:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: skiplist 1.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io skiplist: affected >= 0.0.0-0, < 1.3.0; fixed in 1.3.0

## Suggested inspection (read-only)
- crates.io skiplist: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on skiplist.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0409 (OSV record RUSTSEC-2026-0409 lists affected ranges: crates.io skiplist >=0.0.0-0 <1.3.0 (fixed))

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